ATM (was Re: too many routes)

Fri Sep 12 14:57:53 UTC 1997

Nathan Stratton wrote:
> 
> On Thu, 11 Sep 1997, Vadim Antonov wrote:
> 
> > Quote from Jim Steinhardt's <jsteinha at cisco.com>
> > personal message:
> >
> > >>a) light is slower in dense media
> >
> > >   The index of refraction of glass is 1.5 vs 1.0 for
> > >  a vacuum.  Hence, the speed of light in glass is 2 * 10 **8 m/s.
> >
> > That gives 60 ms RTT on 4000 mile line.
> >
> > Case closed.
> 
> Yep, but you also need to add a few ms for electronics in that 4000 mile
> line. 

  My original point. (Concerning latency)

> We tend to see around 64 - 65 ms delay between our DCA and PAL
> routers.
> 
> rt1.DCA.netrail.net# ping rt1.PAL
> ICMP ECHO rt1.PAL.netrail.net (205.215.45.33):  56 data bytes
> 64 bytes from 205.215.45.33: icmp_seq=0 ttl=255 time=65.764 ms
> 64 bytes from 205.215.45.33: icmp_seq=1 ttl=255 time=64.851 ms
> 64 bytes from 205.215.45.33: icmp_seq=2 ttl=255 time=65.053 ms
> 64 bytes from 205.215.45.33: icmp_seq=3 ttl=255 time=64.994 ms
> ^C

   How may hops is that ping ? I am curious, this is interesting.
(Even if I did get mail bombed by responses...... ;)

   You realize we need to be comparing a *series* of routers, vs a
*series* of ATM
switches. (this is the real world, and we are modelling delivery to
anywhere, not just
1 hop across the continent.)

  It would be interesting to see someone set up a performance test.

Latency/Variability with no hops,
Latency/Variability with 1 router vs 1 switch
Latency/Variability with 2 routers vs 2 switches
Up to about 10. I wonder what that curve would look like ? 
Media would have to be consistent in size (ie DS3, all the way through)

Interesting , no ?

> --- rt1.PAL.netrail.net ICMP ECHO statistics ---
> 4 packets transmitted, 4 packets received, 0% packet loss
> round-trip min/avg/max = 64.851/65.160/65.764 ms
> rt1.DCA.netrail.net#
> 
> Nathan Stratton                             President, CTO, NetRail,Inc.
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> great strength.                                        - Psalm 33:16

Richard